// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

namespace cpp tparquet
namespace java org.apache.parquet.format

/**
 * Types supported by Parquet.  These types are intended to be used in combination
 * with the encodings to control the on disk storage format.
 * For example INT16 is not included as a type since a good encoding of INT32
 * would handle this.
 */
enum Type {
  BOOLEAN = 0;
  INT32 = 1;
  INT64 = 2;
  INT96 = 3;  // deprecated, new Parquet writers should not write data in INT96
  FLOAT = 4;
  DOUBLE = 5;
  BYTE_ARRAY = 6;
  FIXED_LEN_BYTE_ARRAY = 7;
}

/**
 * DEPRECATED: Common types used by frameworks(e.g. hive, pig) using parquet.
 * ConvertedType is superseded by LogicalType.  This enum should not be extended.
 *
 * See LogicalTypes.md for conversion between ConvertedType and LogicalType.
 */
enum ConvertedType {
  /** a BYTE_ARRAY actually contains UTF8 encoded chars */
  UTF8 = 0;

  /** a map is converted as an optional field containing a repeated key/value pair */
  MAP = 1;

  /** a key/value pair is converted into a group of two fields */
  MAP_KEY_VALUE = 2;

  /** a list is converted into an optional field containing a repeated field for its
   * values */
  LIST = 3;

  /** an enum is converted into a BYTE_ARRAY field */
  ENUM = 4;

  /**
   * A decimal value.
   *
   * This may be used to annotate BYTE_ARRAY or FIXED_LEN_BYTE_ARRAY primitive
   * types. The underlying byte array stores the unscaled value encoded as two's
   * complement using bigendian byte order (the most significant byte is the
   * zeroth element). The value of the decimal is the value * 10^{scale}.
   *
   * This must be accompanied by a (maximum) precision and a scale in the
   * SchemaElement. The precision specifies the number of digits in the decimal
   * and the scale stores the location of the decimal point. For example 1.23
   * would have precision 3 (3 total digits) and scale 2 (the decimal point is
   * 2 digits over).
   */
  DECIMAL = 5;

  /**
   * A Date
   *
   * Stored as days since Unix epoch, encoded as the INT32 physical type.
   *
   */
  DATE = 6;

  /**
   * A time
   *
   * The total number of milliseconds since midnight.  The value is stored
   * as an INT32 physical type.
   */
  TIME_MILLIS = 7;

  /**
   * A time.
   *
   * The total number of microseconds since midnight.  The value is stored as
   * an INT64 physical type.
   */
  TIME_MICROS = 8;

  /**
   * A date/time combination
   *
   * Date and time recorded as milliseconds since the Unix epoch.  Recorded as
   * a physical type of INT64.
   */
  TIMESTAMP_MILLIS = 9;

  /**
   * A date/time combination
   *
   * Date and time recorded as microseconds since the Unix epoch.  The value is
   * stored as an INT64 physical type.
   */
  TIMESTAMP_MICROS = 10;


  /**
   * An unsigned integer value.
   *
   * The number describes the maximum number of meaningful data bits in
   * the stored value. 8, 16 and 32 bit values are stored using the
   * INT32 physical type.  64 bit values are stored using the INT64
   * physical type.
   *
   */
  UINT_8 = 11;
  UINT_16 = 12;
  UINT_32 = 13;
  UINT_64 = 14;

  /**
   * A signed integer value.
   *
   * The number describes the maximum number of meaningful data bits in
   * the stored value. 8, 16 and 32 bit values are stored using the
   * INT32 physical type.  64 bit values are stored using the INT64
   * physical type.
   *
   */
  INT_8 = 15;
  INT_16 = 16;
  INT_32 = 17;
  INT_64 = 18;

  /**
   * An embedded JSON document
   *
   * A JSON document embedded within a single UTF8 column.
   */
  JSON = 19;

  /**
   * An embedded BSON document
   *
   * A BSON document embedded within a single BYTE_ARRAY column.
   */
  BSON = 20;

  /**
   * An interval of time
   *
   * This type annotates data stored as a FIXED_LEN_BYTE_ARRAY of length 12
   * This data is composed of three separate little endian unsigned
   * integers.  Each stores a component of a duration of time.  The first
   * integer identifies the number of months associated with the duration,
   * the second identifies the number of days associated with the duration
   * and the third identifies the number of milliseconds associated with
   * the provided duration.  This duration of time is independent of any
   * particular timezone or date.
   */
  INTERVAL = 21;
}

/**
 * Representation of Schemas
 */
enum FieldRepetitionType {
  /** This field is required (can not be null) and each row has exactly 1 value. */
  REQUIRED = 0;

  /** The field is optional (can be null) and each row has 0 or 1 values. */
  OPTIONAL = 1;

  /** The field is repeated and can contain 0 or more values */
  REPEATED = 2;
}

/**
 * A structure for capturing metadata for estimating the unencoded,
 * uncompressed size of data written. This is useful for readers to estimate
 * how much memory is needed to reconstruct data in their memory model and for
 * fine grained filter pushdown on nested structures (the histograms contained
 * in this structure can help determine the number of nulls at a particular
 * nesting level and maximum length of lists).
 */
struct SizeStatistics {
   /**
    * The number of physical bytes stored for BYTE_ARRAY data values assuming
    * no encoding. This is exclusive of the bytes needed to store the length of
    * each byte array. In other words, this field is equivalent to the `(size
    * of PLAINENCODING the byte array values)  (4 bytes * number of values
    * written)`. To determine unencoded sizes of other types readers can use
    * schema information multiplied by the number of nonnull and null values.
    * The number of null/nonnull values can be inferred from the histograms
    * below.
    *
    * For example, if a column chunk is dictionaryencoded with dictionary
    * ["a", "bc", "cde"], and a data page contains the indices [0, 0, 1, 2],
    * then this value for that data page should be 7 (1 + 1 + 2 + 3).
    *
    * This field should only be set for types that use BYTE_ARRAY as their
    * physical type.
    */
   1: optional i64 unencoded_byte_array_data_bytes;
   /**
    * When present, there is expected to be one element corresponding to each
    * repetition (i.e. size=max repetition_level+1) where each element
    * represents the number of times the repetition level was observed in the
    * data.
    *
    * This field may be omitted if max_repetition_level is 0 without loss
    * of information.
    **/
   2: optional list<i64> repetition_level_histogram;
   /**
    * Same as repetition_level_histogram except for definition levels.
    *
    * This field may be omitted if max_definition_level is 0 or 1 without
    * loss of information.
    **/
   3: optional list<i64> definition_level_histogram;
}

/**
 * Bounding box for GEOMETRY or GEOGRAPHY type in the representation of min/max
 * value pair of coordinates from each axis.
 */
struct BoundingBox {
  1: required double xmin;
  2: required double xmax;
  3: required double ymin;
  4: required double ymax;
  5: optional double zmin;
  6: optional double zmax;
  7: optional double mmin;
  8: optional double mmax;
}

/** Statistics specific to Geometry and Geography logical types */
struct GeospatialStatistics {
  /** A bounding box of geospatial instances */
  1: optional BoundingBox bbox;
  /** Geospatial type codes of all instances, or an empty list if not known */
  2: optional list<i32> geospatial_types;
}

/**
 * Statistics per row group and per page
 * All fields are optional.
 */
struct Statistics {
   /**
    * DEPRECATED: min and max value of the column. Use min_value and max_value.
    *
    * Values are encoded using PLAIN encoding, except that variablelength byte
    * arrays do not include a length prefix.
    *
    * These fields encode min and max values determined by signed comparison
    * only. New files should use the correct order for a column's logical type
    * and store the values in the min_value and max_value fields.
    *
    * To support older readers, these may be set when the column order is
    * signed.
    */
   1: optional binary max;
   2: optional binary min;
   /** 
    * Count of null values in the column.
    *
    * Writers SHOULD always write this field even if it is zero (i.e. no null value)
    * or the column is not nullable.
    * Readers MUST distinguish between null_count not being present and null_count == 0.
    * If null_count is not present, readers MUST NOT assume null_count == 0.
    */
   3: optional i64 null_count;
   /** count of distinct values occurring */
   4: optional i64 distinct_count;
   /**
    * Lower and upper bound values for the column, determined by its ColumnOrder.
    *
    * These may be the actual minimum and maximum values found on a page or column
    * chunk, but can also be (more compact) values that do not exist on a page or
    * column chunk. For example, instead of storing "Blart Versenwald III", a writer
    * may set min_value="B", max_value="C". Such more compact values must still be
    * valid values within the column's logical type.
    *
    * Values are encoded using PLAIN encoding, except that variablelength byte
    * arrays do not include a length prefix.
    */
   5: optional binary max_value;
   6: optional binary min_value;
   /** If true, max_value is the actual maximum value for a column */
   7: optional bool is_max_value_exact;
   /** If true, min_value is the actual minimum value for a column */
   8: optional bool is_min_value_exact;
}

/** Empty structs to use as logical type annotations */
struct StringType {}  // allowed for BYTE_ARRAY, must be encoded with UTF8
struct UUIDType {}    // allowed for FIXED[16], must be encoded as raw UUID bytes
struct MapType {}     // see LogicalTypes.md
struct ListType {}    // see LogicalTypes.md
struct EnumType {}    // allowed for BYTE_ARRAY, must be encoded with UTF8
struct DateType {}    // allowed for INT32
struct Float16Type {} // allowed for FIXED[2], must be encoded as raw FLOAT16 bytes (see LogicalTypes.md)

/**
 * Logical type to annotate a column that is always null.
 *
 * Sometimes when discovering the schema of existing data, values are always
 * null and the physical type can't be determined. This annotation signals
 * the case where the physical type was guessed from all null values.
 */
struct NullType {}    // allowed for any physical type, only null values stored

/**
 * Decimal logical type annotation
 *
 * Scale must be zero or a positive integer less than or equal to the precision.
 * Precision must be a nonzero positive integer.
 *
 * To maintain forwardcompatibility in v1, implementations using this logical
 * type must also set scale and precision on the annotated SchemaElement.
 *
 * Allowed for physical types: INT32, INT64, FIXED_LEN_BYTE_ARRAY, and BYTE_ARRAY.
 */
struct DecimalType {
  1: required i32 scale
  2: required i32 precision
}

/** Time units for logical types */
struct MilliSeconds {}
struct MicroSeconds {}
struct NanoSeconds {}
union TimeUnit {
  1: MilliSeconds MILLIS
  2: MicroSeconds MICROS
  3: NanoSeconds NANOS
}

/**
 * Timestamp logical type annotation
 *
 * Allowed for physical types: INT64
 */
struct TimestampType {
  1: required bool isAdjustedToUTC
  2: required TimeUnit unit
}

/**
 * Time logical type annotation
 *
 * Allowed for physical types: INT32 (millis), INT64 (micros, nanos)
 */
struct TimeType {
  1: required bool isAdjustedToUTC
  2: required TimeUnit unit
}

/**
 * Integer logical type annotation
 *
 * bitWidth must be 8, 16, 32, or 64.
 *
 * Allowed for physical types: INT32, INT64
 */
struct IntType {
  1: required i8 bitWidth
  2: required bool isSigned
}

/**
 * Embedded JSON logical type annotation
 *
 * Allowed for physical types: BYTE_ARRAY
 */
struct JsonType {
}

/**
 * Embedded BSON logical type annotation
 *
 * Allowed for physical types: BYTE_ARRAY
 */
struct BsonType {
}

/**
 * Embedded Variant logical type annotation
 */
struct VariantType {
  // The version of the variant specification that the variant was
  // written with.
  1: optional i8 specification_version
}

/** Edge interpolation algorithm for Geography logical type */
enum EdgeInterpolationAlgorithm {
  SPHERICAL = 0;
  VINCENTY = 1;
  THOMAS = 2;
  ANDOYER = 3;
  KARNEY = 4;
}

/**
 * Embedded Geometry logical type annotation
 *
 * Geospatial features in the WellKnown Binary (WKB) format and edges interpolation
 * is always linear/planar.
 *
 * A custom CRS can be set by the crs field. If unset, it defaults to "OGC:CRS84",
 * which means that the geometries must be stored in longitude, latitude based on
 * the WGS84 datum.
 *
 * Allowed for physical type: BYTE_ARRAY.
 *
 * See Geospatial.md for details.
 */
struct GeometryType {
  1: optional string crs;
}

/**
 * Embedded Geography logical type annotation
 *
 * Geospatial features in the WKB format with an explicit (nonlinear/nonplanar)
 * edges interpolation algorithm.
 *
 * A custom geographic CRS can be set by the crs field, where longitudes are
 * bound by [180, 180] and latitudes are bound by [90, 90]. If unset, the CRS
 * defaults to "OGC:CRS84".
 *
 * An optional algorithm can be set to correctly interpret edges interpolation
 * of the geometries. If unset, the algorithm defaults to SPHERICAL.
 *
 * Allowed for physical type: BYTE_ARRAY.
 *
 * See Geospatial.md for details.
 */
struct GeographyType {
  1: optional string crs;
  2: optional EdgeInterpolationAlgorithm algorithm;
}

/**
 * LogicalType annotations to replace ConvertedType.
 *
 * To maintain compatibility, implementations using LogicalType for a
 * SchemaElement must also set the corresponding ConvertedType (if any)
 * from the following table.
 */
union LogicalType {
  1:  StringType STRING       // use ConvertedType UTF8
  2:  MapType MAP             // use ConvertedType MAP
  3:  ListType LIST           // use ConvertedType LIST
  4:  EnumType ENUM           // use ConvertedType ENUM
  5:  DecimalType DECIMAL     // use ConvertedType DECIMAL + SchemaElement.{scale, precision}
  6:  DateType DATE           // use ConvertedType DATE

  // use ConvertedType TIME_MICROS for TIME(isAdjustedToUTC = *, unit = MICROS)
  // use ConvertedType TIME_MILLIS for TIME(isAdjustedToUTC = *, unit = MILLIS)
  7:  TimeType TIME

  // use ConvertedType TIMESTAMP_MICROS for TIMESTAMP(isAdjustedToUTC = *, unit = MICROS)
  // use ConvertedType TIMESTAMP_MILLIS for TIMESTAMP(isAdjustedToUTC = *, unit = MILLIS)
  8:  TimestampType TIMESTAMP

  // 9: reserved for INTERVAL
  10: IntType INTEGER         // use ConvertedType INT_* or UINT_*
  11: NullType UNKNOWN        // no compatible ConvertedType
  12: JsonType JSON           // use ConvertedType JSON
  13: BsonType BSON           // use ConvertedType BSON
  14: UUIDType UUID           // no compatible ConvertedType
  15: Float16Type FLOAT16     // no compatible ConvertedType
  16: VariantType VARIANT     // no compatible ConvertedType
  17: GeometryType GEOMETRY   // no compatible ConvertedType
  18: GeographyType GEOGRAPHY // no compatible ConvertedType
}

/**
 * Represents a element inside a schema definition.
 *   if it is a group (inner node) then type is undefined and num_children is defined
 *   if it is a primitive type (leaf) then type is defined and num_children is undefined
 * the nodes are listed in depth first traversal order.
 */
struct SchemaElement {
  /** Data type for this field. Not set if the current element is a nonleaf node */
  1: optional Type type;

  /** If type is FIXED_LEN_BYTE_ARRAY, this is the byte length of the values.
   * Otherwise, if specified, this is the maximum bit length to store any of the values.
   * (e.g. a low cardinality INT col could have this set to 3).  Note that this is
   * in the schema, and therefore fixed for the entire file.
   */
  2: optional i32 type_length;

  /** repetition of the field. The root of the schema does not have a repetition_type.
   * All other nodes must have one */
  3: optional FieldRepetitionType repetition_type;

  /** Name of the field in the schema */
  4: required string name;

  /** Nested fields.  Since thrift does not support nested fields,
   * the nesting is flattened to a single list by a depthfirst traversal.
   * The children count is used to construct the nested relationship.
   * This field is not set when the element is a primitive type
   */
  5: optional i32 num_children;

  /**
   * DEPRECATED: When the schema is the result of a conversion from another model.
   * Used to record the original type to help with cross conversion.
   *
   * This is superseded by logicalType.
   */
  6: optional ConvertedType converted_type;

  /**
   * DEPRECATED: Used when this column contains decimal data.
   * See the DECIMAL converted type for more details.
   *
   * This is superseded by using the DecimalType annotation in logicalType.
   */
  7: optional i32 scale
  8: optional i32 precision

  /** When the original schema supports field ids, this will save the
   * original field id in the parquet schema
   */
  9: optional i32 field_id;

  /**
   * The logical type of this SchemaElement
   *
   * LogicalType replaces ConvertedType, but ConvertedType is still required
   * for some logical types to ensure forwardcompatibility in format v1.
   */
  10: optional LogicalType logicalType
}

/**
 * Encodings supported by Parquet.  Not all encodings are valid for all types.  These
 * enums are also used to specify the encoding of definition and repetition levels.
 * See the accompanying doc for the details of the more complicated encodings.
 */
enum Encoding {
  /** Default encoding.
   * BOOLEAN  1 bit per value. 0 is false; 1 is true.
   * INT32  4 bytes per value.  Stored as littleendian.
   * INT64  8 bytes per value.  Stored as littleendian.
   * FLOAT  4 bytes per value.  IEEE. Stored as littleendian.
   * DOUBLE  8 bytes per value.  IEEE. Stored as littleendian.
   * BYTE_ARRAY  4 byte length stored as little endian, followed by bytes.
   * FIXED_LEN_BYTE_ARRAY  Just the bytes.
   */
  PLAIN = 0;

  /** Group VarInt encoding for INT32/INT64.
   * This encoding is deprecated. It was never used
   */
  //  GROUP_VAR_INT = 1;

  /**
   * Deprecated: Dictionary encoding. The values in the dictionary are encoded in the
   * plain type.
   * in a data page use RLE_DICTIONARY instead.
   * in a Dictionary page use PLAIN instead
   */
  PLAIN_DICTIONARY = 2;

  /** Group packed run length encoding. Usable for definition/repetition levels
   * encoding and Booleans (on one bit: 0 is false; 1 is true.)
   */
  RLE = 3;

  /** Bit packed encoding.  This can only be used if the data has a known max
   * width.  Usable for definition/repetition levels encoding.
   */
  BIT_PACKED = 4;

  /** Delta encoding for integers. This can be used for int columns and works best
   * on sorted data
   */
  DELTA_BINARY_PACKED = 5;

  /** Encoding for byte arrays to separate the length values and the data. The lengths
   * are encoded using DELTA_BINARY_PACKED
   */
  DELTA_LENGTH_BYTE_ARRAY = 6;

  /** Incrementalencoded byte array. Prefix lengths are encoded using DELTA_BINARY_PACKED.
   * Suffixes are stored as delta length byte arrays.
   */
  DELTA_BYTE_ARRAY = 7;

  /** Dictionary encoding: the ids are encoded using the RLE encoding
   */
  RLE_DICTIONARY = 8;

  /** Encoding for fixedwidth data (FLOAT, DOUBLE, INT32, INT64, FIXED_LEN_BYTE_ARRAY).
      K bytestreams are created where K is the size in bytes of the data type.
      The individual bytes of a value are scattered to the corresponding stream and
      the streams are concatenated.
      This itself does not reduce the size of the data but can lead to better compression
      afterwards.

      Added in 2.8 for FLOAT and DOUBLE.
      Support for INT32, INT64 and FIXED_LEN_BYTE_ARRAY added in 2.11.
   */
  BYTE_STREAM_SPLIT = 9;
}

/**
 * Supported compression algorithms.
 *
 * Codecs added in format version X.Y can be read by readers based on X.Y and later.
 * Codec support may vary between readers based on the format version and
 * libraries available at runtime.
 *
 * See Compression.md for a detailed specification of these algorithms.
 */
enum CompressionCodec {
  UNCOMPRESSED = 0;
  SNAPPY = 1;
  GZIP = 2;
  LZO = 3;
  BROTLI = 4;  // Added in 2.4
  LZ4 = 5;     // DEPRECATED (Added in 2.4)
  ZSTD = 6;    // Added in 2.4
  LZ4_RAW = 7; // Added in 2.9
}

enum PageType {
  DATA_PAGE = 0;
  INDEX_PAGE = 1;
  DICTIONARY_PAGE = 2;
  DATA_PAGE_V2 = 3;
}

/**
 * Enum to annotate whether lists of min/max elements inside ColumnIndex
 * are ordered and if so, in which direction.
 */
enum BoundaryOrder {
  UNORDERED = 0;
  ASCENDING = 1;
  DESCENDING = 2;
}

/** Data page header */
struct DataPageHeader {
  /**
   * Number of values, including NULLs, in this data page.
   *
   * If a OffsetIndex is present, a page must begin at a row
   * boundary (repetition_level = 0). Otherwise, pages may begin
   * within a row (repetition_level > 0).
   **/
  1: required i32 num_values

  /** Encoding used for this data page **/
  2: required Encoding encoding

  /** Encoding used for definition levels **/
  3: required Encoding definition_level_encoding;

  /** Encoding used for repetition levels **/
  4: required Encoding repetition_level_encoding;

  /** Optional statistics for the data in this page **/
  5: optional Statistics statistics;
}

struct IndexPageHeader {
  // TODO
}

/**
 * The dictionary page must be placed at the first position of the column chunk
 * if it is partly or completely dictionary encoded. At most one dictionary page
 * can be placed in a column chunk.
 **/
struct DictionaryPageHeader {
  /** Number of values in the dictionary **/
  1: required i32 num_values;

  /** Encoding using this dictionary page **/
  2: required Encoding encoding

  /** If true, the entries in the dictionary are sorted in ascending order **/
  3: optional bool is_sorted;
}

/**
 * New page format allowing reading levels without decompressing the data
 * Repetition and definition levels are uncompressed
 * The remaining section containing the data is compressed if is_compressed is true
 **/
struct DataPageHeaderV2 {
  /** Number of values, including NULLs, in this data page. **/
  1: required i32 num_values
  /** Number of NULL values, in this data page.
      Number of nonnull = num_values  num_nulls which is also the number of values in the data section **/
  2: required i32 num_nulls
  /**
   * Number of rows in this data page. Every page must begin at a
   * row boundary (repetition_level = 0): rows must **not** be
   * split across page boundaries when using V2 data pages.
   **/
  3: required i32 num_rows
  /** Encoding used for data in this page **/
  4: required Encoding encoding

  // repetition levels and definition levels are always using RLE (without size in it)

  /** Length of the definition levels */
  5: required i32 definition_levels_byte_length;
  /** Length of the repetition levels */
  6: required i32 repetition_levels_byte_length;

  /**  Whether the values are compressed.
  Which means the section of the page between
  definition_levels_byte_length + repetition_levels_byte_length + 1 and compressed_page_size (included)
  is compressed with the compression_codec.
  If missing it is considered compressed */
  7: optional bool is_compressed = true;

  /** Optional statistics for the data in this page **/
  8: optional Statistics statistics;
}

/** Blockbased algorithm type annotation. **/
struct SplitBlockAlgorithm {}
/** The algorithm used in Bloom filter. **/
union BloomFilterAlgorithm {
  /** Blockbased Bloom filter. **/
  1: SplitBlockAlgorithm BLOCK;
}

/** Hash strategy type annotation. xxHash is an extremely fast noncryptographic hash
 * algorithm. It uses 64 bits version of xxHash.
 **/
struct XxHash {}

/**
 * The hash function used in Bloom filter. This function takes the hash of a column value
 * using plain encoding.
 **/
union BloomFilterHash {
  /** xxHash Strategy. **/
  1: XxHash XXHASH;
}

/**
 * The compression used in the Bloom filter.
 **/
struct Uncompressed {}
union BloomFilterCompression {
  1: Uncompressed UNCOMPRESSED;
}

/**
  * Bloom filter header is stored at beginning of Bloom filter data of each column
  * and followed by its bitset.
  **/
struct BloomFilterHeader {
  /** The size of bitset in bytes **/
  1: required i32 numBytes;
  /** The algorithm for setting bits. **/
  2: required BloomFilterAlgorithm algorithm;
  /** The hash function used for Bloom filter. **/
  3: required BloomFilterHash hash;
  /** The compression used in the Bloom filter **/
  4: required BloomFilterCompression compression;
}

struct PageHeader {
  /** the type of the page: indicates which of the *_header fields is set **/
  1: required PageType type

  /** Uncompressed page size in bytes (not including this header) **/
  2: required i32 uncompressed_page_size

  /** Compressed (and potentially encrypted) page size in bytes, not including this header **/
  3: required i32 compressed_page_size

  /** The 32bit CRC checksum for the page, to be be calculated as follows:
   *
   *  The standard CRC32 algorithm is used (with polynomial 0x04C11DB7,
   *   the same as in e.g. GZip).
   *  All page types can have a CRC (v1 and v2 data pages, dictionary pages,
   *   etc.).
   *  The CRC is computed on the serialization binary representation of the page
   *   (as written to disk), excluding the page header. For example, for v1
   *   data pages, the CRC is computed on the concatenation of repetition levels,
   *   definition levels and column values (optionally compressed, optionally
   *   encrypted).
   *  The CRC computation therefore takes place after any compression
   *   and encryption steps, if any.
   *
   * If enabled, this allows for disabling checksumming in HDFS if only a few
   * pages need to be read.
   */
  4: optional i32 crc

  // Headers for page specific data.  One only will be set.
  5: optional DataPageHeader data_page_header;
  6: optional IndexPageHeader index_page_header;
  7: optional DictionaryPageHeader dictionary_page_header;
  8: optional DataPageHeaderV2 data_page_header_v2;
}

/**
 * Wrapper struct to store key values
 */
 struct KeyValue {
  1: required string key
  2: optional string value
}

/**
 * Sort order within a RowGroup of a leaf column
 */
struct SortingColumn {
  /** The ordinal position of the column (in this row group) **/
  1: required i32 column_idx

  /** If true, indicates this column is sorted in descending order. **/
  2: required bool descending

  /** If true, nulls will come before nonnull values, otherwise,
   * nulls go at the end. */
  3: required bool nulls_first
}

/**
 * statistics of a given page type and encoding
 */
struct PageEncodingStats {

  /** the page type (data/dic/...) **/
  1: required PageType page_type;

  /** encoding of the page **/
  2: required Encoding encoding;

  /** number of pages of this type with this encoding **/
  3: required i32 count;

}

/**
 * Description for column metadata
 */
struct ColumnMetaData {
  /** Type of this column **/
  1: required Type type

  /** Set of all encodings used for this column. The purpose is to validate
   * whether we can decode those pages. **/
  2: required list<Encoding> encodings

  /** Path in schema **/
  3: required list<string> path_in_schema

  /** Compression codec **/
  4: required CompressionCodec codec

  /** Number of values in this column **/
  5: required i64 num_values

  /** total byte size of all uncompressed pages in this column chunk (including the headers) **/
  6: required i64 total_uncompressed_size

  /** total byte size of all compressed, and potentially encrypted, pages 
   *  in this column chunk (including the headers) **/
  7: required i64 total_compressed_size

  /** Optional key/value metadata **/
  8: optional list<KeyValue> key_value_metadata

  /** Byte offset from beginning of file to first data page **/
  9: required i64 data_page_offset

  /** Byte offset from beginning of file to root index page **/
  10: optional i64 index_page_offset

  /** Byte offset from the beginning of file to first (only) dictionary page **/
  11: optional i64 dictionary_page_offset

  /** optional statistics for this column chunk */
  12: optional Statistics statistics;

  /** Set of all encodings used for pages in this column chunk.
   * This information can be used to determine if all data pages are
   * dictionary encoded for example **/
  13: optional list<PageEncodingStats> encoding_stats;

  /** Byte offset from beginning of file to Bloom filter data. **/
  14: optional i64 bloom_filter_offset;

  /** Size of Bloom filter data including the serialized header, in bytes.
   * Added in 2.10 so readers may not read this field from old files and
   * it can be obtained after the BloomFilterHeader has been deserialized.
   * Writers should write this field so readers can read the bloom filter
   * in a single I/O.
   */
  15: optional i32 bloom_filter_length;

  /**
   * Optional statistics to help estimate total memory when converted to inmemory
   * representations. The histograms contained in these statistics can
   * also be useful in some cases for more finegrained nullability/list length
   * filter pushdown.
   */
  16: optional SizeStatistics size_statistics;

  /** Optional statistics specific for Geometry and Geography logical types */
  17: optional GeospatialStatistics geospatial_statistics;
}

struct EncryptionWithFooterKey {
}

struct EncryptionWithColumnKey {
  /** Column path in schema **/
  1: required list<string> path_in_schema

  /** Retrieval metadata of column encryption key **/
  2: optional binary key_metadata
}

union ColumnCryptoMetaData {
  1: EncryptionWithFooterKey ENCRYPTION_WITH_FOOTER_KEY
  2: EncryptionWithColumnKey ENCRYPTION_WITH_COLUMN_KEY
}

struct ColumnChunk {
  /** File where column data is stored.  If not set, assumed to be same file as
    * metadata.  This path is relative to the current file.
    **/
  1: optional string file_path

  /** Deprecated: Byte offset in file_path to the ColumnMetaData
   *
   * Past use of this field has been inconsistent, with some implementations
   * using it to point to the ColumnMetaData and some using it to point to
   * the first page in the column chunk. In many cases, the ColumnMetaData at this
   * location is wrong. This field is now deprecated and should not be used.
   * Writers should set this field to 0 if no ColumnMetaData has been written outside
   * the footer.
   */
  2: required i64 file_offset = 0

  /** Column metadata for this chunk. Some writers may also replicate this at the
   * location pointed to by file_path/file_offset.
   * Note: while marked as optional, this field is in fact required by most major
   * Parquet implementations. As such, writers MUST populate this field.
   **/
  3: optional ColumnMetaData meta_data

  /** File offset of ColumnChunk's OffsetIndex **/
  4: optional i64 offset_index_offset

  /** Size of ColumnChunk's OffsetIndex, in bytes **/
  5: optional i32 offset_index_length

  /** File offset of ColumnChunk's ColumnIndex **/
  6: optional i64 column_index_offset

  /** Size of ColumnChunk's ColumnIndex, in bytes **/
  7: optional i32 column_index_length

  /** Crypto metadata of encrypted columns **/
  8: optional ColumnCryptoMetaData crypto_metadata

  /** Encrypted column metadata for this chunk **/
  9: optional binary encrypted_column_metadata
}

struct RowGroup {
  /** Metadata for each column chunk in this row group.
   * This list must have the same order as the SchemaElement list in FileMetaData.
   **/
  1: required list<ColumnChunk> columns

  /** Total byte size of all the uncompressed column data in this row group **/
  2: required i64 total_byte_size

  /** Number of rows in this row group **/
  3: required i64 num_rows

  /** If set, specifies a sort ordering of the rows in this RowGroup.
   * The sorting columns can be a subset of all the columns.
   */
  4: optional list<SortingColumn> sorting_columns

  /** Byte offset from beginning of file to first page (data or dictionary)
   * in this row group **/
  5: optional i64 file_offset

  /** Total byte size of all compressed (and potentially encrypted) column data 
   *  in this row group **/
  6: optional i64 total_compressed_size
  
  /** Row group ordinal in the file **/
  7: optional i16 ordinal
}

/** Empty struct to signal the order defined by the physical or logical type */
struct TypeDefinedOrder {}

/**
 * Union to specify the order used for the min_value and max_value fields for a
 * column. This union takes the role of an enhanced enum that allows rich
 * elements (which will be needed for a collationbased ordering in the future).
 *
 * Possible values are:
 * * TypeDefinedOrder  the column uses the order defined by its logical or
 *                      physical type (if there is no logical type).
 *
 * If the reader does not support the value of this union, min and max stats
 * for this column should be ignored.
 */
union ColumnOrder {

  /**
   * The sort orders for logical types are:
   *   UTF8  unsigned bytewise comparison
   *   INT8  signed comparison
   *   INT16  signed comparison
   *   INT32  signed comparison
   *   INT64  signed comparison
   *   UINT8  unsigned comparison
   *   UINT16  unsigned comparison
   *   UINT32  unsigned comparison
   *   UINT64  unsigned comparison
   *   DECIMAL  signed comparison of the represented value
   *   DATE  signed comparison
   *   FLOAT16  signed comparison of the represented value (*)
   *   TIME_MILLIS  signed comparison
   *   TIME_MICROS  signed comparison
   *   TIMESTAMP_MILLIS  signed comparison
   *   TIMESTAMP_MICROS  signed comparison
   *   INTERVAL  undefined
   *   JSON  unsigned bytewise comparison
   *   BSON  unsigned bytewise comparison
   *   ENUM  unsigned bytewise comparison
   *   LIST  undefined
   *   MAP  undefined
   *   VARIANT  undefined
   *   GEOMETRY  undefined
   *   GEOGRAPHY  undefined
   *
   * In the absence of logical types, the sort order is determined by the physical type:
   *   BOOLEAN  false, true
   *   INT32  signed comparison
   *   INT64  signed comparison
   *   INT96 (only used for legacy timestamps)  undefined(+)
   *   FLOAT  signed comparison of the represented value (*)
   *   DOUBLE  signed comparison of the represented value (*)
   *   BYTE_ARRAY  unsigned bytewise comparison
   *   FIXED_LEN_BYTE_ARRAY  unsigned bytewise comparison
   *
   * (+) While the INT96 type has been deprecated, at the time of writing it is
   *    still used in many legacy systems. If a Parquet implementation chooses
   *    to write statistics for INT96 columns, it is recommended to order them
   *    according to the legacy rules:
   *     compare the last 4 bytes (days) as a littleendian 32bit signed integer
   *     if equal last 4 bytes, compare the first 8 bytes as a littleendian
   *      64bit signed integer (nanos)
   *    See https://github.com/apache/parquetformat/issues/502 for more details
   *
   * (*) Because the sorting order is not specified properly for floating
   *     point values (relations vs. total ordering) the following
   *     compatibility rules should be applied when reading statistics:
   *      If the min is a NaN, it should be ignored.
   *      If the max is a NaN, it should be ignored.
   *      If the min is +0, the row group may contain 0 values as well.
   *      If the max is 0, the row group may contain +0 values as well.
   *      When looking for NaN values, min and max should be ignored.
   * 
   *     When writing statistics the following rules should be followed:
   *      NaNs should not be written to min or max statistics fields.
   *      If the computed max value is zero (whether negative or positive),
   *       `+0.0` should be written into the max statistics field.
   *      If the computed min value is zero (whether negative or positive),
   *       `0.0` should be written into the min statistics field.
   */
  1: TypeDefinedOrder TYPE_ORDER;
}

struct PageLocation {
  /** Offset of the page in the file **/
  1: required i64 offset

  /**
   * Size of the page, including header. Sum of compressed_page_size and header
   * length
   */
  2: required i32 compressed_page_size

  /**
   * Index within the RowGroup of the first row of the page. When an
   * OffsetIndex is present, pages must begin on row boundaries
   * (repetition_level = 0).
   */
  3: required i64 first_row_index
}

/**
 * Optional offsets for each data page in a ColumnChunk.
 *
 * Forms part of the page index, along with ColumnIndex.
 *
 * OffsetIndex may be present even if ColumnIndex is not.
 */
struct OffsetIndex {
  /**
   * PageLocations, ordered by increasing PageLocation.offset. It is required
   * that page_locations[i].first_row_index < page_locations[i+1].first_row_index.
   */
  1: required list<PageLocation> page_locations
  /**
   * Unencoded/uncompressed size for BYTE_ARRAY types.
   *
   * See documention for unencoded_byte_array_data_bytes in SizeStatistics for
   * more details on this field.
   */
  2: optional list<i64> unencoded_byte_array_data_bytes
}

/**
 * Optional statistics for each data page in a ColumnChunk.
 *
 * Forms part the page index, along with OffsetIndex.
 *
 * If this structure is present, OffsetIndex must also be present.
 *
 * For each field in this structure, <field>[i] refers to the page at
 * OffsetIndex.page_locations[i]
 */
struct ColumnIndex {
  /**
   * A list of Boolean values to determine the validity of the corresponding
   * min and max values. If true, a page contains only null values, and writers
   * have to set the corresponding entries in min_values and max_values to
   * byte[0], so that all lists have the same length. If false, the
   * corresponding entries in min_values and max_values must be valid.
   */
  1: required list<bool> null_pages

  /**
   * Two lists containing lower and upper bounds for the values of each page
   * determined by the ColumnOrder of the column. These may be the actual
   * minimum and maximum values found on a page, but can also be (more compact)
   * values that do not exist on a page. For example, instead of storing ""Blart
   * Versenwald III", a writer may set min_values[i]="B", max_values[i]="C".
   * Such more compact values must still be valid values within the column's
   * logical type. Readers must make sure that list entries are populated before
   * using them by inspecting null_pages.
   */
  2: required list<binary> min_values
  3: required list<binary> max_values

  /**
   * Stores whether both min_values and max_values are ordered and if so, in
   * which direction. This allows readers to perform binary searches in both
   * lists. Readers cannot assume that max_values[i] <= min_values[i+1], even
   * if the lists are ordered.
   */
  4: required BoundaryOrder boundary_order

  /**
   * A list containing the number of null values for each page 
   *
   * Writers SHOULD always write this field even if no null values
   * are present or the column is not nullable.
   * Readers MUST distinguish between null_counts not being present 
   * and null_count being 0.
   * If null_counts are not present, readers MUST NOT assume all 
   * null counts are 0.
   */
  5: optional list<i64> null_counts

  /**
   * Contains repetition level histograms for each page
   * concatenated together.  The repetition_level_histogram field on
   * SizeStatistics contains more details.
   *
   * When present the length should always be (number of pages *
   * (max_repetition_level + 1)) elements.
   *
   * Element 0 is the first element of the histogram for the first page.
   * Element (max_repetition_level + 1) is the first element of the histogram
   * for the second page.
   **/
   6: optional list<i64> repetition_level_histograms;
   /**
    * Same as repetition_level_histograms except for definitions levels.
    **/
   7: optional list<i64> definition_level_histograms;
}

struct AesGcmV1 {
  /** AAD prefix **/
  1: optional binary aad_prefix

  /** Unique file identifier part of AAD suffix **/
  2: optional binary aad_file_unique

  /** In files encrypted with AAD prefix without storing it,
   * readers must supply the prefix **/
  3: optional bool supply_aad_prefix
}

struct AesGcmCtrV1 {
  /** AAD prefix **/
  1: optional binary aad_prefix

  /** Unique file identifier part of AAD suffix **/
  2: optional binary aad_file_unique

  /** In files encrypted with AAD prefix without storing it,
   * readers must supply the prefix **/
  3: optional bool supply_aad_prefix
}

union EncryptionAlgorithm {
  1: AesGcmV1 AES_GCM_V1
  2: AesGcmCtrV1 AES_GCM_CTR_V1
}

/**
 * Description for file metadata
 */
struct FileMetaData {
  /** Version of this file **/
  1: required i32 version

  /** Parquet schema for this file.  This schema contains metadata for all the columns.
   * The schema is represented as a tree with a single root.  The nodes of the tree
   * are flattened to a list by doing a depthfirst traversal.
   * The column metadata contains the path in the schema for that column which can be
   * used to map columns to nodes in the schema.
   * The first element is the root **/
  2: required list<SchemaElement> schema;

  /** Number of rows in this file **/
  3: required i64 num_rows

  /** Row groups in this file **/
  4: required list<RowGroup> row_groups

  /** Optional key/value metadata **/
  5: optional list<KeyValue> key_value_metadata

  /** String for application that wrote this file.  This should be in the format
   * <Application> version <App Version> (build <App Build Hash>).
   * e.g. impala version 1.0 (build 6cf94d29b2b7115df4de2c06e2ab4326d721eb55)
   **/
  6: optional string created_by

  /**
   * Sort order used for the min_value and max_value fields in the Statistics
   * objects and the min_values and max_values fields in the ColumnIndex
   * objects of each column in this file. Sort orders are listed in the order
   * matching the columns in the schema. The indexes are not necessary the same
   * though, because only leaf nodes of the schema are represented in the list
   * of sort orders.
   *
   * Without column_orders, the meaning of the min_value and max_value fields
   * in the Statistics object and the ColumnIndex object is undefined. To ensure
   * welldefined behaviour, if these fields are written to a Parquet file,
   * column_orders must be written as well.
   *
   * The obsolete min and max fields in the Statistics object are always sorted
   * by signed comparison regardless of column_orders.
   */
  7: optional list<ColumnOrder> column_orders;

  /** 
   * Encryption algorithm. This field is set only in encrypted files
   * with plaintext footer. Files with encrypted footer store algorithm id
   * in FileCryptoMetaData structure.
   */
  8: optional EncryptionAlgorithm encryption_algorithm

  /** 
   * Retrieval metadata of key used for signing the footer. 
   * Used only in encrypted files with plaintext footer. 
   */ 
  9: optional binary footer_signing_key_metadata
}

/** Crypto metadata for files with encrypted footer **/
struct FileCryptoMetaData {
  /** 
   * Encryption algorithm. This field is only used for files
   * with encrypted footer. Files with plaintext footer store algorithm id
   * inside footer (FileMetaData structure).
   */
  1: required EncryptionAlgorithm encryption_algorithm
    
  /** Retrieval metadata of key used for encryption of footer, 
   *  and (possibly) columns **/
  2: optional binary key_metadata
}